Mechanical actuator package



Dec. 26, 1967 J. J. PHILLIPS 3,359,804

MECHANICAL ACTUATOR PACKAGE Filed Oct. 11, 1965 46 Fig.1.

52 Fl 2 J g wn Fig. 3.

John J. Phi I lips,

INVENTOR.

ATTORNEY.

United States Patent 3,359,804 MECHANICAL ACTUATOR PACKAGE John J.Phillips, Rolling Hills, Calif., assignor to Gray & Huleguard, SantaMonica, Calif., a corporation of California Filed Oct. 11, 1965, Ser.No. 494,851 16 Claims. (Cl. 74-2) ABSTRACT OF THE DISCLOSURE Theactuator includes a pair of members which may be forced apart, forexample by means of a heavily loaded spring. These members are securedtogether by a latch means which includes a plurality of resilient springfingers. Keeper means maintains the resilient fingers in the lockedposition whereby the actuator package is maintained in a fully loadedcondition. The keeper means includes a multipiece spool and anelectrically conductive wire around the spool. When an electric currentcirculates through the keeper wire the tensile strength of the wire veryrapidly falls below the tension in the wire whereby the wire suddenlybreaks as a result of a mechanical failure, the spool separates andfrees the fingers whereby the actuator package is released.

The present invention relates to electromechanical actuators and moreparticularly to fast acting actuators capable of providing large forces.

It is frequently desirable to remotely or automatically actuate a deviceby physically moving a member. One means of accomplishing this is toemploy a solenoid or servomechanism wherein an electric current iscirculated through a coil coupled to a magnetic armature. Although suchmechanisms are effective to provide the desired control, they arenormally very expensive. Also when it is necessary toproduce a largeforce the mechanism is not only very bulky and heavy, but also requireslarge amounts of power and/or are slow acting. As a conse quencesolenoids and servomechanisms are not entirely suitable for all types ofapplications wherein a remote control is required.

Another means of accomplishing a remote control is to employ apyrotechnic device such as a squib. Such devices can be considerablysmaller and lighter than a solenoid or servomechanism and produce largerforces. However, they are very susceptible to premature or accidentaldischarge whereby severe damage and possible personal injury or deathmay occur. It can thus be appreciated that pyrotechnic devices areextremely dangerous and require a considerable amount of specialhandling etc. Also, it is impossible to test a pyrotechnic device forreliability without destroying the device. As a result even in thoseinstances where a high degree of reliability is necessary it isimpossible to guarantee operation.

More recently the foregoing difliculties and disadvantages have beenovercome by employing electromechanical devices such as disclosed andclaimed in US. Patent- #3,163,732 entitled Electrically Fused SpringPackage filed in the names of John R. Abbott and John J. Phillips. In adevice of this nature a spring is maintained in a loaded condition by anelectrically responsive keeper wire. When an electrical currentcirculates through the wire it becomes hot and its tensile strengthdecreases below the tension produced therein by the loaded spring. Theweakened keeper wire breaks from this tension and the spring is releasedto actuate any suitable device.

The foregoing type of actuator package is well suited for its intendeduse and is capable of providing a large working force from a very smallpackage within an ex- "ice tremely short interval following the start ofthe current. However, the amount of tension in the keeper wire is afunction of the amount of force produced by the spring. As a consequencewhen a very strong or heavily loaded spring has been employed it wasnecessary to employ a correspondingly strong keeper wire. This in turnrequires a correspondingly larger current for heating the wire and/or acorrespondingly longer period of time for the wire to separate.

The present invention provides means for overcoming the foregoingdifficulties, More particularly the present invention provides anelectromechanical device of the foregoing nature wherein the spring maybe heavily loaded to provide an extremely strong force while at the sametime employing a keeper wire that is very small and capable ofseparating in an extremely short time in response to a very smallcurrent.

In the limited number of embodiments of the invention disclosed hereinthis is accomplished by providing a member having a plurality ofresilient fingers and a drive member that is moveably disposed inside ofthe fingers. The fingers and the drive member include coacting camsurfaces that prevent the drive member moving until the fingers areexpanded radially outwardly. A heavily loaded spring reacts between thetwo members whereby to force them in opposite directions. The springalso applies a force on the cam surfaces that tends to force the fingersradially outwardly and release the members. However, a large number ofturns of a keeper wire encompasses the fingers and prevents the fingersexpanding whereby the spring cannot move the members. Since there are alarge numbr of turns of keeper wire, a large mechanical advantage isprovided whereby a small keeper Wire can restrain an extremely largeforce produced by a very heavily loaded spring. As a consequence thekeeper wire will separate in an extremely short interval in response toa small current. Means are also provided for insuring that the separatedwire instantly disengages the fingers whereby the members are released.

These and other features and advantages of the present invention willbecome readily apparent from the follow ing detailed description of alimited number of embodiments thereof, particularly when taken inconnection therewith the accompanying drawings wherein like referencenumerals refer to like parts and wherein FIGURE 1 is a cross sectionalview of an actuator package embodying one form of the present invention,

FIGURE 2 is a side view, on a greatly enlarged scale, of a keeper wireemployed in the actuator package of FIGURE 1.

FIGURE 3 is a cross sectional view of an actuator package embodyinganother form of the present invention.

FIGURE 4 is a cross sectional view of an actuator package embodying astill further form of the present invention.

Referring to the drawings in more detail and particularly to FIGURES 1and 2, the present invention is particularly adapted to be embodied in asmall electromechanical package 10 capable of producing an extremelylarge force within an extremely short interval following the circulationof an electrical current therethrough.

More particularly, the actuator package 10 includes a first or supportmember 12 having a mounting flange 14. This flange 14 may be rigidlysecured to a fixed reaction member such as a bulkhead 16 etc. As willbecome apparent subsequently the actuator package may be adapted toproduce a very large force, for exampleseveral hundred pounds.Accordingly, the bulkhead 16 i should be sufficiently strong towithstand such a force.

The support member 12 includes a barrel 18 that extends at right anglesto the mounting flange 14. A passage 3 210 having a generallycylindrical surface extends axially through the barrel 18. In additionthe barrel 18 includes a plurality of cantilever fingers 22. The innerends of the fingers 22 form an integral part of the flange 14 wherebythey are rigidly held in place.

The fingers 22 may be formed by any suitable means such as by cuttingthe barrel 18 longitudinally at a plurality of equally spaced points.The resultant fingers 22 will thereby be separated from each other by acorresponding number of longitudinally extending slots 24. The fingers22 will thus act as springs whereby the outer ends 26 thereof may beresiliently deflected between a radially inner position and a radiallyouter position. The fingers 22 may naturally remain in either position.However, in the present instance they remain in the inner position, i.e.the position of FIGURE 1.

The package also includes a second or drive member 28 that is moveablerelative to the support member 12. In the present embodiment the drivemember 28 fits into the passage 2% extending through the center of thebarrel 18. Preferably the exterior surface of the drive member 28 iseffective to slide freely along the cylindrical surface inside of thebarrel 18. A plurality of guide pins 30 or similar devices may projectoutwardly from the drive member 28 so as to extend into and through theslots 24. This will be effective to prevent the second member 28rotating as it travels axially through the barrel 18.

A stop such as a pin or flange 32 maybe provided on the inner end of thedrive member 28. This stop 32 engages the end of the support member 12or the bulkhead 16 upon which it is mounted. This is effective to limitthe stroke of the drive member and prevent it from passing completelythrough the barrel 18.

A drive spring 34 is disposed concentrically about the exterior of thebarrel 18 with one end engaging the flange 14 and the other end engagingthe pins 38. This spring 34 will thus react between the support anddrive members 12 and 28 and tends to bias the drive member 28 axiallythrough the barrel 18 (to the left as seen in FIGURE 1). Normally it isdesirable for the actuator package 10 to produce a large force, forexample several hundred pounds. Under these circumstances the spring 34is very stiff. Although the spring 34 may be of any desired form such asone or more helical springs, it has been found a stack of Bellevillewashers provides very large forces in a small space.

The stop 32 limits the amount of travel of the second member andprevents its being forced out of the barrel 18. In order to maintain thedrive member 28 locked in a loaded'or cocked position with the spring 34fully loaded, a latch 36 may be provided. In the present instance thislatch includes a tapered portion adjacent the outer end of the drivemember 28. This tapered portion forms an annular ramp or cam surface 38.In addition the outer ends 26 of the fingers 24 include tapered portionsthat provide 'a set of ramps or cam shoulders 40 on the inner surfacesthereof.

When the resilient fingers 22 are in their radially inner position, theinside diameters of the shoulders 40 are less than the outside diameterof the drive member 28. As a consequence the cam surface 38 on the drivemember 28 will engage the set of cam shoulders 49. As long as thefingers 22 remain in their inner position the drive member 28 will beunable to pass beyond the ends26 of the fingers 22. However, when thefingers 22 are spread radially outwardly, the inside diameter of the camshoultend to expand the various fingers 22 toward the radially outerposition whereby the spring 34 may force the drive member 28 past theshoulders 40.

In order to prevent the fingers 22 spreading outwardly and releasing thedrive member 28, a keeper 42 is provided for maintaining the fingers 22compressed into the radially inner position. In the present instancethis keeper 42 is in the form of an electrically conductive wire 44wound around the exterior of the fingers 22. As long as the wire 44 isunbroken the fingers 22 will remain locked in the inner position.However, as soon as the wire 44 breaks the fingers 22 are released andthe spring 34 will force the drive member 28 axially of the barrel 18.

In orderto control breaking of the wire 44, the Wire may be connected toa source 46 of electrical current. When the switch 48 is closed, thesource 46 is effective to circulate enough current through the wire 44to heat it enough to cause it to separate. The current may be largeenough to melt the wire 44. However, as the temperature of the Wire 44increases beyond a predetermined level the tensile strength of the wiredecreases. It is to be noted that a large amount of tension is producedin the wire 44 by the spring 34 and the coaction of the cam surface 38and the shoulders 40 spreading the fingers 22. As a result, when thecurrent heats the wire 44 above this critical level the tensile strengthwill fall below the tension and the wire 44 will break.

It is to be noted that the wire 44 must have a sufiicient tensilestrength when it is at normal temperatures to Withstand the tensionforce resulting from the spreading of the fingers 22. However it isdesirable to maintain the diameter of the wire 44 as small as possible.This will enable a small amount of current to be used and insure .thewire 44 rapidly reaching the critical failure temperature. In order topermit a small diameter wire with a low tensile strength to be employed,the keeper wire 44 may be Wound around the fingers 22 a large number oftimes. For example, the wire 44 may include as much as 50 turns or more.

By a proper choice of angles on the cam surface 38 and shoulders 40 andthe proper number of turns a very large mechanical advantage may beobtained. By way of example, it has been found that a wire 44 with atensile strength of about 4 pounds may restrain a spring 34 having aforce of about 400 pounds. Thus a mechanical advantage of to 1 isobtained. As a consequence of this large advantage the wire 44 may besmall enough to be heated by a small current, for example 1 to 5amperes. Moreover, because of its small size the wire 44 will heat upand separate in a very short interval, for example a few milliseconds orless.

As soon as the wire 44 separates it is possible for the fingers 22 toexpand radially and allow the drive member 28 to perform the desiredoperation. However, it has been found that if the wire 44 shouldseparate near one end a large amount of friction results from the largenumber of turns of the wire 44 sliding on the exterior of the barrel 18.This makes the unwinding of the keeper wire 44 from the fingers 28 andthe release of the drive member 22 slow and unpredictable. Accordingly,if a large number of turns of small wire are to be employed, it is alsodesirable to provide means for insuring that the wire 44 rapidly unwindsas soon as it separates. Although this may be accomplished in a widevariety of ways in the present instance the keeper wire 44 is coupled toa resilient member that will unwind the wire 44 as soon as it isreleased. In the present embodiment the wire 44 is threaded through ahollowtubing 50 of the type commonly employed for making hypodermicneedles. Such a tubing 50 is sulficiently flexible to ermit it to betightly wrapped around the exterior of the fingers 22. However, it isvery resilient and straightens out rapidly when released.

Such a keeper 42 is shown in FIGURE 2. Normally the tubing is notcontinuous. Instead it has a short break which exposes a short segment52 of the wire 44. In the encased portions the current flows throughboth the tubing 50 and the wire 44 whereas in the exposed segment 52 allof the current goes through the wire 44. As a consequence the exposedsegment 52 of the wire 44 will heat up and weaken more rapidly than therest of the wire. As a consequence the most probable point of separationis in the region of the exposed segment 52. It is to be noted that thetubing 50 will tend to reinforce the portions of the wire it surroundsand thereby further increase the probability of the separation occurringat the segment 52.

In order to employ this package 10 it is first loaded. This isaccomplished by moving the drive member 28 inwardly to load the spring34. The fingers 22 are then compressed inwardly so that the shoulders 40will engage the surface 38 and lock the drive member 28 in position.Following this the encased keeper wire 44 is wrapped around the fingers22 a suificient number of times to Withstand the expanding forceproduced by load spring 34. The package 16 is now fully loaded and thedrive member 28 may be connected to a load to be actuated thereby.

In order to actuate the package 16 after it has been loaded, a currentis circulated through the keeper wire 44. This current will cause thetemperature of the exposed segment 52 to rapidly rise above the criticaltemperature. The wire 44 will then separate. When this occurs the tubing50 will immediately tend to unwrap itself from the fingers 22. Thefingers 22 will thereby be instantly released and the drive member 28freed to move axially through the barrel 18 with the full force of thespring 34.

As an alternative the embodiment of the actuator package 60 shown inFIGURE 3 may be employed. This package 66 is very similar to thepreceding package 10 in that it includes a support member 62 having abarrel 64 with a plurality of resilient fingers 66. The support member62 is adapted to be attached to any desired structure such as abulkhead. A drive member 68 is slideably disposed inside of the barrel64 for movement axially thereof.

A passage 70 extends axially of the drive member 68 for receiving a loadspring 72. This spring 72 reacts between the support member 62 and thedrive member 68 whereby the drive member 68 is biased axially of thepassage 70. The outer end of the drive member 68 includes a ramp or camsurface 74 which is effective to engage similar cam shoulders 76 on theinsides of the fingers 66. When the fingers 66 are in the radially innerposition shown, the drive member 68 cannot move axially through thebarrel 64. However the force from the loaded spring 72 tends to forcethe fingers 66 radially outwardly. When the fingers 66 do move to theradially outer position the drive member 68 is released. The spring 72then forces the drive member 68 outwardly and produces the desiredoperation.

In order to prevent the drive member 68 moving through the fingers 66 asuitable keeper 78 is provided for maintaining the finger 66 compressedinto the radially inner position. Although the keeper 78 may be the sametype employed in the first embodiment, in this embodiment the keeper 78includes a spring ribbon S wrapped around the fingers 66. By employing alarge number of turns, for example or turns or more, the spring ribbon80 may be relatively light weight and very resilient, similar to themain spring in a watch. Such a spring 80 may be tightly wound around thefingers 66 for retaining them locked into position. However as soon asit i released, the spring 72 instantly unwinds and expands radiallyoutwardly and frees the fingers 66.

To prevent the untimely unwinding of this spring 80, a currentresponsive keeper wire 82 is attached to this spring 80. When this Wire82 is at room temperature, the tensile strength is just adequate toretain the spring 80 in the tightly wound position. However when acurrent flows through this wire 82, the temperature rapidly rises into acritical range wherein the tensile strength decreases. As soon as thestrength falls sufficiently, the wire 82 breaks and the spring 80 willimmediately unwind from around the fingers 66. A portion of thisunwinding will be attributable to the force resulting from the springforcing the drive member 68 against the cam shoulders 76 on the fingers66. However, a large part of the unwinding force will result from thenatural resiliency of the spring 80. It will thus be seen that eventhough a large numberof turns are employed the spring 80 will rapidlyrelease the fingers 66.

As a further alternative the package of FIGURE 4 may be employed. Thispackage 90 includes a support member 92 having a fastening means such asa clevis 94 for being attached to a load bearing member such as abulkhead etc. A second, or drive member 96 is provided which alsoincludes fastening means such as a clevis 98 for attaching the package90 to a load to be supported but released.

The first member 92 includes a shank 100 on one end while the secondmember 96 includes a barrel 102 having a passage 104 into which theshank 100 may fit. Fastening means such as complementary threads 106 maybe provided on the barrel 102 and the shank 100 for securing the twomembers 92 and 96 together.

The barrel 102 includes a plurality of fingers 108 which surround thepassage 104 and are moveable between a radially inner position andradially outer position. Normally the fingers 108 move toward the outerposition. When the fingers 108 are in the inner position, the threads106 on the fingers 108 and the shank 100 will firmly lock the members 92and 96 together. However when the fingers 108 are in the outer position,the threads 106 will separate and the two members 92 and 96 will bedisconnected.

In order to maintain the fingers 108 in the inner position and securethe members 92 and 96 together a suitable keeper 110 is provided. Thekeeper 110 fits around the fingers 108 and maintains them compressedinwardly into the inner position. Although the keeper 110 may beidentical to either of the preceding embodiments, in this em bodimentthe keeper 110 includes a bobbin or spool '112 that fits over theexterior of; the fingers 108. This spool 112 includes several piecessuch as three or four that may be placed together to form a cylinder.However, the pieces may rapidly separate and release the fingers 108.

A thermal Wire 114 is wrapped around the pieces a large number of timesso as to form a single structure that is capable of retaining thefingers 108 locked in position. Th s wire 114 may be of any desiredvariety. However It includes a small wire and a surrounding tubingsimilar to that in FIGURE 2.

border to utilize this package 90, the pieces of the bobbin or spool 112are placed together and the keeper wire 114 wound there around until astrong self-supportmg keeper unit 110 is formed. This keeper 110 maythen be slipped onto the exterior of the fingers :108 and moved to thenouter ends 116, this will compress the fingers 108 1nwardly and retainthem in the inner position. Following this the two members 92 and 96 arethreaded together until the overall length of the package 90 is suitablefor securing the load to the support. After the assembled package 90 issecured in position it may be actuated by circulating a current throughthe keeper wire 114. When the wire 114 separates, the resiliency of thefingers 108 will separate the pieces of the spool 112 and move into theouter position. When this occurs the two members 92 and 96 will bereleased.

It may be appreciated that the spool 112 and wire 114 wrappedtherearound forms an easily handled preassembled keeper unit 110. Thiskeeper 110 may be easily slipped over the fingers of any of the actuatorpackages 10, 60 or 90 and as a consequence is suitable for installationwhere the device is to be repeatedly employed.

Although only a limited number of embodiments of the present inventionare disclosed herein, it will be readily apparent to persons experiencedin the art that numerous changes may be made without departing from theinvention. For example, the arrangement and configuration of the varioussupport and the drive members may be varied. Also the form of the keepermay be varied. Accordingly, the foregoing disclosures and descriptionsare for illustrative purposes only and do not in any way limit thepresent invention which is defined only by the claims which follow.

I claim:

1. An electromechanical actuator package including the combination of anouter member,

an inner member moveably disposed inside of said outer member,

a plurality of resilient fingers on the outer member surrounding saidinner member and being moveable between a radially inner position andthe radially outer position,

a cam surface on the inner member,

cam shoulders on said fingers positioned to engage said cam surface whenthe fingers are in the inner position and prevent the members movingrelatively to each other, the cam shoulders being effective to disengagethe cam surface and release said members for relative movement when thefingers are in the radially outer position,

spring means connected to said members and forcing the inner memberthrough said fingers, said spring forcing the cam surface against saidshoulders whereby the fingers are forced radially outwardly towards thesecond portion,

a keeper wrapped around said fingers and keeping them in the innerposition, I

said keeper including a wire having a tensile strength at ambienttemperatures that is greater than tension produced in said wire by theexpanding fingers, said keeper including a resilient sleeve around saidWire to unwind the keeper when the wire separates.

2. An electromechanical actuator package including the combination of apair of members moveable relative to each other,

a cam surface on one of said members,

a plurality of resilient fingers on the other of said mem bers, saidfingers being movable between a radially inner position and a radiallyouter position,

cam shoulders on said fingers positioned to engage the cam surface whenthe fingers are in the inner position and prevent the members movingrelatively to each other, the cam shoulder being effective to disengagethe cam surface and release said members for relative movement when thefingers are in the radially outer position,

an expandable keeper spool encompassing the fingers and retaining themin the inner position,

a keeper wire wrapped around the keeper spool, said wire having atensile strength at ambient temperature greater than the tension in saidWire, said wire having a tensile strength at an elevated temperaturethat is less than said tension.

3. An electromechanical actuator package including the combination of aplurality of resilient fingers, said fingers being moveable between aradially inner position and a radially outer position,

a member moveable relative to the fingers,

cam means on said fingers and the member, said cam means beingpositioned to engage each other and lock the member in a fixed positionwhen the fingers are in the inner position, said cam means beingeffective to separate and release said member when the fingers are inthe radially outer position,

means exerting a force on said member tending to move said memberrelative to the fingers, said cam means being effective to spread saidfingers into the radially outer position, and

a keeper includin g a center wire and a surrounding reif! silientsleeve, said center wire having a high tensile strength at ambienttemperature and a low tensile strength above a predetermined elevatedtemperature, said sleeve being effective to unwind said keeper from saidfingers when said wire separates.

4. An electromechanical actuator package including the combination of aplurality of resilient fingers, said fingers being moveable between aradially inner position and a radially outer position,

a member moveable relative to the fingers,

cam means on said fingers and the member, said cam means being effectiveto engage each other and lock the fingers and member together when thefingers are in the inner position, said cam means being effective toseparate and release said member when the fingers are in the radiallyouter position,

means exerting a force on said member tending to move said memberrelative to the fingers, said cam means being effective to spread saidfingers into the radially outer position,

a keeper spool encompassing the fingers and maintaining them in theradially inner position, said keeper spool being expandable to free saidfingers for movement into the radially outer position, and

a keeper wire encompassing said spool and having a high tensile strengthat ambient temperatures and a low tensile strength at a predeterminedelevated temperature.

5. An electromechanical actuator package including the combination of aplurality of resilient fingers, said fingers being moveable between aradially inner position and a radially outer position,

a member moveable relative to the fingers,

cam means on said fingers and member, said cam means being effective toengage each other and lock the fingers and member together when thefingers are in the inner position, said cam means being effective toseparate and release said member when the fingers are in the radiallyouter position,

means exerting a force on said member tending to move said memberrelative to the fingers, said cam means being effective to spread saidfingers into the radially outer position,

a keeper wire wrapped around said fingers and having a high tensilestrength at ambient temperature and a low tensile strength above apredetermined elevated temperature, the number of turns of said wirebeing large enough to reduce the tension in the Wire produced by the cammeans to less than the tensile strength of the wire at ambienttemperature but few enough to maintain the tension in said keeper wiregreater than the low tensile strength whereby said wire will break, and

means to unwind said keeper wire from said fingers when said wirebreaks.

6. An electromechanical actuator package including the combination of aplurality of resilient fingers moveable between a radially innerposition and a radially outer position,

a member moveable relative to said fingers,

means on said fingers positioned to engage the member when the fingersare in the inner position and prevent movement of the member, said meansbeing effective to disengage said member when the fingers are in theradially outer position and release the member for movement,

means exert-ing a force on said member tending to move said body memberrelative to the fingers and biasing the fingers radially outwardly, and

a keeper wrapped around the fingers and effective to maintain thefingers in the inner position, said keeper including means effective toseparate in response to combination of a plurality of resilient fingersmoveable between a radially inner position and radially outer position,

a member moveable relative to said fingers,

said fingers when in the inner position engaging said member andpreventing movement thereof, said fingers when in the outer positionreleasing the member for movement,

a plurality of turns of a keeper wire wrapped around the fingers tomaintain the fingers in the inner position, said wire being breakable torelease the fingers for movement to the outer position, and

resilient means coupled to said keeper wire to unwind the keeper wirefrom the fingers when said wire breaks.

8. An electromechanical actuator package including the combination of aplurality of resilient fingers moveable between a radially innerposition and a radially outer position,

a member moveable relative to the fingers,

means on said fingers positioned to engage the member when the fingersare in the inner position and prevent movement of the member, said meansbeing eifective to disengage said member when the fingers are in theradially outer position and release the member for movement,

means exerting a force on said member tending to move said body memberrelative to the fingers and biasing the fingers toward the radiallyouter position,

a keeper wire having a high tensile strength at ambient temperature anda low tensile strength above a predetermined elevated temperature, aplurality of turns of said wire wrapped around the fingers until thetension produced in the wire by the spreading of the fingers is lessthan the tensile strength of the wire at ambient temperature but isgreater than the tensile strength of the wire at the elevatedtemperature whereby said keeper wire separates at the elevatedtemperature, and

mean eifective to unwind said keeper wire when it separates.

9. An electromechanical actuator package including the combination of anouter member having a passage extending axially therethrough,

an inner member disposed in said passage moveable relative to the outermember,

a plurality of resilient fingers on the outer member surrounding theinner member, said fingers being moveable between a radially innerposition and the radially outer position,

a cam surface on the inner member,

cam shoulders on said fingers positioned to engage the cam surface whenthe fingers are in the inner position and retain the inner member inposition, the cam shoulders being effective to disengage the cam surfaceand release said inner member for movement when the fingers are in theradially outer position,

spring means connected to said members and forcing the cam surfaceagainst said shoulders whereby the fingers are forced radially outwardlytowards the second portion, and

a plurality of turns of a keeper wrapped around the fingers, said keeperhaving a tensile strength at ambient temperature greater than tensionproduced in said keeper by the spring means, said keeper having atensile strength at an elevated temperature that is less than saidtension whereby the keeper breaks at said elevated temperature, saidkeeper being resilient and effective to rapidly unwind when it breaks.

10. An electromechanical actuator package including the combination of apair of members moveable relative to each other,

latch means on one of said members moveable between a locked positionwherein said members are secured together and an unlocked positionwherein said members are released and free to move,

means exerting a force on said members tending to move them in oppositedirections and biasing the latch means into the unlocked position,

a keeper retaining the latch means in the locked position against thebiasing force, said keeper being effective to separate and release thelatch means when the temperature of the keeper exceeds a predeterminedlevel, and

spring means in said keeper to release said latch means when the keeperseparates.

11. An electromechanical actuator package including the combination of apair of members moveable relative to each other,

latch means on one of said members moveable between a locked positionwherein said members are secured together and an unlocked positionwherein said members are free to move,

means exerting a force on said members tending to move them in oppositedirections and biasing the latch means into the unlocked position,

a keeper wire encompassing the latch means and retaining the latch meansin the locked position against the biasing force, said wire beingeffective to separate and release the latch means when the temperatureexceeds a predetermined temperature, and

a resilient sleeve encompassing the keeper wire, said sleeve beingeffective to remove the keeper Wire from the latch means when the wireseparates.

12. An electromechanical actuator package including the combination offirst and second members moveable relative to each other,

latch means on the first member moveable between a locked position andan unlocked position, said latch means when in the locked positionengaging the second member and securing said members together,

means exerting a force on said members biasing them in oppositedirections and biasing the latch means into the unlocked position,

a multipiece keeper on the latch means for retaining the latch means inthe locked position against the biasing force, and

a temperature responsive member maintaining the pieces of the keepertogether, said temperature responsive member being effective to separateat an elevated temperature and allow the pieces of the keeper toseparate and release the latch means.

13. An electromechanical actuator package including the combination ofthe combination of a pair of members moveable relative to each other,

a plurality of fingers on the first member engaging the second memberand retaining them locked together,

means tending to move said members in opposite directions and spreadsaid fingers radially outwardly to release the bodies for relativemovement, and

a keeper wrapped around the fingers, said keeper including a center wirethat weakens and separates at an elevated temperature and a resilientsleeve around the wire that unwraps the keeper from the fingers when thewire separates.

15. An electromechanical actuator package including the combination of apair of members moveable relative to each other,

a plurality of fingers on the first member engaging the second memberand retaining the members locked together,

means tending to move said members in opposite directions and spreadsaid fingers radially outwardly to release the members for relativemovement, and

a keeper encompassing said fingers and maintaining them in engagementwith the first member, said keeper including a plurality of separablepieces on said fingers and a wire wrapped around said pieces, said wirehaving a large tensile strength at ambient temperature and a low tensilestrength above a predetermined temperature, said wire encompassing thepieces a sufficient number of times to reduce the tension producedtherein from the spreading of the fingers to less than said largetensile strength.

16.An electromechanical actuator package including the combination of apair of separate load bearing members moveable relative to each other inresponse to a force applied to said members,

a keeper for maintaining said members secured together, said keeperincluding a plurality of separable pieces biased radially outwardly whensaid members are secured together,

- an electrically conductive temperature responsive member encompassingsaid keeper, said temperature responsive member having a tension thereinand being effective to maintain said pieces biased radially inwardlytoward each other whereby said load bearing members are secured togetherby said keeper,

said temperature responsive member when at ambient temperatures having atensile strength greater than said tension, said temperature responsivemember when at an elevated temperature having a tensile strength lessthan said tension, and

means coupled to said temperature responsive member whereby an electriccurrent may be circulated through said temperature responsive memberuntil said member is heated above elevated temperature and separateswhereby the pieces of said keeper separate and said load bearing membersare released.

References Cited UNITED STATES PATENTS 3,163,732 12/1964 Abbott 200123 XMILTON KAUFMAN, Primary Examiner.

1. AN ELECTROMECHANICAL ACTUATOR PACKAGE INCLUDING THE COMBINATION OF ANOUTER MEMBER, AN INNER MEMBER MOVEABLY DISPOSED INSIDE OF SAID OUTERMEMBER, A PLURALITY OF RESILIENT FINGERS ON THE OUTER MEMBER SURROUNDINGSAID INNER MEMBER AND BEING MOVEABLE BETWEEN A RADIALLY INNER POSITIONAND THE RADIALLY OUTER POSITION, A CAM SURFACE ON THE INNER MEMBER, CAMSHOULDERS ON SAID FINGERS POSITIONED TO ENGAGE SAID CAM SURFACE WHEN THEFINGERS ARE IN THE INNER POSITION AND PREVENT THE MEMBERS MOVINGRELATIVELY TO EACH OTHER, THE CAM SHOULDERS BEING EFFECTIVE TO DISENGAGETHE CAM SURFACE AND RELEASE SAID MEMBERS FOR RELATIVE MOVEMENT WHEN THEFINGERS ARE IN THE RADIALLY OUTER POSITION, SPRING MEANS CONNECTED TOSAID MEMBERS AND FORCING THE INNER MEMBER THROUGH SAID FINGERS, SAIDSPRING FORCING THE CAM SURFACE AGAINST SAID SHOULDERS WHEREBY THEFINGERS ARE FORCED RADIALLY OUTWARDLY TOWARDS THE SECOND PORTION, AKEEPER WRAPPED AROUND SAID FINGERS AND KEEPING THEM IN THE INNERPOSITION, SAID KEEPER INCLUDING A WIRE HAVING A TENSILE STRENGTH ATAMBIENT TEMPERATURES THAT IS GREATER THAN TENSION PRODUCED IN SAID WIREBY THE EXPANDING FINGERS, SAID KEEPER INCLUDING A RESILIENT SLEEVEAROUND SAID WIRE TO UNWIND THE KEEPER WHEN THE WIRE SEPARATES.